Subject: Re: Need help designing a circuit
X-Newsreader: Microsoft Outlook Express 6.00.2800.1106
Date: Sat, 2 Nov 2002 21:03:15 -0500
NNTP-Posting-Date: Sat, 02 Nov 2002 21:37:48 EST
Organization: Bell Sympatico
Actually, that's a pretty good idea. Several PIRS would not be needed, and
its pretty easy to stop a turntable once a signal is received. The PIR that
I'm using is one from a exterior light, so its pretty sensitive, and has a
pretty wide field of view. The turntable will be rotating pretty fast, so I
doubt anything will be missed that is moving within its field of view.
"Bill Sloman" wrote in message
> "Neil" wrote in message
> > Ok...I'm not very bright...I haven't embraced microcontrollers, and like
> > do things with good old fashioned components and IC's. Keeping this in
> > I need a circuit that senses the position of an object, then turns on a
> > motor to power a turntable to turn toward the object. I have several
> > detectors that will be placed in the center of the turntable. So I need
> > circuit that will sense which PIR has detected the object, and then
> > off once the turntable is has turned towards the direction of the
> > PIR.. It doesn't need to have any sort of accuracy, as long as the
> > stops close to the subject(within about +/- 20 or 30 degrees). The
> > switching can be either electro mechanical, or use LED Emitter/
> > Any ideas?.
> > Thanks in advance.
> You don't so much need a circuit as an algorithm. You have "a couple" of
> passive infra-red (PIR) sensors mounted on a turntable, and you want a
> circuit which will do something when one of the PIR sensors has "detected"
> an object.
> You don't specify the aceeptance angle of the PIR sensors, and and you
> specify what sort of signal the PIR sensor is producing when it detects
> object you want to detect (whatever it is).
> The econimical way of doing this job is with a single sensor on a rotating
> turntable - as the turnatable rotates the the single scanner scans
> everything. When it "detects" something - it's output signal moves
> significantly outside the range generated by random noise in the
> and moving non-objects in the field of view - you stop the turntable.
> For more class, you rotate the turntable with a stepper motor, and don't
> stop the turntable immediately, but merely note the position (or start
> counting steps) and allow the turntable to continue to rotate until the
> anomalous signal sinks back into insignificance, after which you reverse
> turntable back through half the number of steps, and then stop it.
> Once you've got the rotating turntable, extra sensnors are a waste of
> Advice on the sort of switches to use depends on you telling us how you
> rotate the turntable, and how big the turntable actually is. My guess
> be a turntable out of a an audio system but even that covers a wide range
> Bill Sloman, Nijmegen